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Chapter 45. Chemical Signals in Animals. Hormones. Hormones are chemical signals. The endocrine system consists of: Endocrine cells which are hormone-secreting cells and Endocrine glands which are hormone-secreting organs. Specific target cells respond to specific hormones.

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Chapter 45

Chemical Signals in Animals


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Hormones

  • Hormones are chemical signals.

    • The endocrine system consists of:

      • Endocrine cells which are hormone-secreting cells and

      • Endocrine glands which are hormone-secreting organs.

  • Specific target cells respond to specific hormones.


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Primary Function of Hormones

  • Homeostasis

  • Growth and Development

  • Reproduction

  • Energy Metabolism

  • Behavior


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stimulates

glucose release from liver

glucagon from pancreas

stimulates

inhibits

blood glucose high

Negative Feedback Loop

blood glucose low



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hormones

endocrine cell

receptor protein

target cell

Mechanism of Action on Target Cells

response


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hormones

endocrine cell

intracellular receptor

target cell

Mechanism of Action on Target Cells

response


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Tropic vs Nontropic Hormones

Tropic hormones- stimulate the production and secretion of hormones by other endocrine glands; ex. TSH

Nontropic hormones- stimulates cellular growth, metabolism, or other functions; ex. thyroxine


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Invertebrate nervous systems clearly illustrate endocrine and nervous system interactions

  • Invertebrates have a wide variety of hormones that are involved in the regulation of homeostasis.


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  • An example from hydra: and nervous system interactions

    • One hormone stimulate asexual reproduction.

    • Another hormone prevents sexual reproduction.

  • An example from a mollusk:

    • The hormone that regulates egg laying also inhibits feeding and locomotion.


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    • Arthropods have extensive endocrine systems regulating molting in insects and crustaceans.

      • The regulation of molting in insects.

        • Ecdysone also promotes the development of adult features.

        • Neurosecretory cells in the brain produce Prothoracicotropic hormone (PTTH), which regulates the secretion of ecdysone.

      • Juvenile hormone (JH) promotes the retention of larval characteristics.


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    • Different molting in insects and crustaceans. signal-transduction pathways in different cells can lead to different responses to the same signal.


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    Frog Metamorphosis molting in insects and crustaceans.

    thyroxin


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    Major Endocrine Organs molting in insects and crustaceans.

    Major endocrine glands:

    Hypothalamus

    Pineal gland

    Fig. 45-10

    Pituitary gland

    Organs containing

    endocrine cells:

    Thyroid gland

    Thymus

    Parathyroid glands

    Heart

    Liver

    Adrenal

    glands

    Stomach

    Pancreas

    Kidney

    Testes

    Small

    intestine

    Kidney

    Ovaries


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    pineal gland molting in insects and crustaceans.

    hypothalamus

    pituitary gland

    Endocrine Organs of the Brain


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    Pineal Gland molting in insects and crustaceans.

    Produces melatonin (synthesized from seratonin, a derivative of tryptophan)

    • Secreted directly in CSF to blood

    • High levels at night make us sleepy; low level during day

    • Pineal gland is stimulated by darkness and inhibited by light

    • Function in regulating circadian rhythms (sleep, body temp, appetite)  biological clock


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    hypothalamus molting in insects and crustaceans.

    anterior pituitary

    posterior pituitary

    Pituitary Gland


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    Posterior Pituitary molting in insects and crustaceans.

    Hypothalamus

    Posterior Pituitary

    Anterior Pituitary


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    Hormones of the molting in insects and crustaceans.

    Posterior Pituitary

    Antidiuretic Hormone (ADH)

    Oxytocin (+ feedback)


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    Anterior Pituitary molting in insects and crustaceans.

    Hypothalamus

    Posterior Pituitary

    Anterior Pituitary


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    Hormones of the molting in insects and crustaceans.

    Anterior Pituitary

    • Growth Hormone (GH)

      • Dwarfism

      • Gigantism & Acromegaly

    • Thyroid Stimulating Hormone (TSH)

    • Adrenocorticotropic Hormone (ACTH)

    • Gonadotropins (FSH, ICSH, LH)

    • Prolactin (PRL)

    • Melanocyte-stimulating Hormone (MSH)


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    Growth Hormone (GH) molting in insects and crustaceans.

    • Acts on the liver, stimulating it to release several polypeptide hormones.

    • Stimulates amino acid uptake and protein synthesis in target cells.

    • Ultimately stimulates cell growth (cell size and number), especially in muscle and bone.

    • Also stimulates fat breakdown.


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    strenuous exercise molting in insects and crustaceans.

    GH Levels

    sleep

    awake


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    Dwarfism molting in insects and crustaceans.

    hyposecretion of GH

    Little People Big World

    Kenadie - worlds smallest girl due to primordial dwarfism


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    Gigantism molting in insects and crustaceans.

    hypersecretion of GH

    Bao Xishun, a 7ft 8.95in herdsman from Inner Mongolia


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    Acromegaly molting in insects and crustaceans.

    hypersecretion of GH

    7 ft 1 ¼ inches


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    Thyroid-Stimulating Hormone (TSH) molting in insects and crustaceans.

    • Acts on the thyroid gland, stimulating it to release T3 & T4

    • These thyroid hormones increase glucose catabolism and body heat production.

    • Negative feedback mechanism involved in regulating levels.


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    Adrenocorticotropic Hormone (ACTH) molting in insects and crustaceans.

    • Acts on the adrenal cortex, stimulating it to secrete glucocorticoids (e.g., cortisol).

    • Glucocorticoids promote the synthesis of glucose from noncarbohydrate sources such as amino acids, and fatty acids

    • Negative feedback mechanism involved in regulating levels.


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    Thyroid Gland molting in insects and crustaceans.

    larynx

    thyroid

    trachea


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    Thyroid Follicles molting in insects and crustaceans.


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    Thyroid Hormones molting in insects and crustaceans.

    Thyroid gland selectively uptakes iodine to produce T3 & T4

    • Thyroxine (T4)

    • Triiodothyronine (T3)

    • Both control metabolic rate and cellular oxidation

    • Calcitonin (from parafolicular cells)- lowers blood CA ++ levels and causes CA++ reabsorption in bone


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    Thyroid Hormone Regulation molting in insects and crustaceans.


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    Thyroid Disorders molting in insects and crustaceans.

    • Hyperthyroidism (Grave’s, Goiter)

    • Hypothyroidism (Cretinism, Myxedima)


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    Goiter molting in insects and crustaceans.

    Lack of iodine in diet

    hyposecretion of T3 & T4


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    Cretinism molting in insects and crustaceans.

    hyposecretion of T3 & T4


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    Myxedema molting in insects and crustaceans.hyposecretion of T3 & T4

    After thyroid treatment

    myxedema


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    Exophthalmos- molting in insects and crustaceans.hyperthyroidism


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    Parathyroid Glands molting in insects and crustaceans.


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    Parathyroid Hormone (PTH) molting in insects and crustaceans.

    • PTH release:

    • stimulates osteoclasts

    • enhances reabsorption of Ca++ by kidneys

    • increases absorption of Ca++ by intestinal mucosal cells

    • Hyperparathyroidism- too much Ca++ drawn out of bone; could be due to tumor

    • Hypoparathyroidism- most often follow parathyroid gland trauma or after removal of thyroid--- tetany, muscle twitches, convulsions; if untreatedrespiratory paralysis and death


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    PTH Effects molting in insects and crustaceans.


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    Pancreas molting in insects and crustaceans.


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    Pancreas molting in insects and crustaceans.

    • Regulates glucose uptake by cells

    • Controlled via negative feedback: insulin & glucagon

    • Blood sugar level: 90 mg/mL


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    Islets of Langerhan molting in insects and crustaceans.


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    Insulin molting in insects and crustaceans.

    • Produced by the  cells of the Islets of Langerhan

    • Catalyze oxidation of glucose for ATP production

    • Lowers blood glucose levels by promoting transport of glucose into cells.

    • Stimulates glucose uptake by the liver and muscle cells.

    • Stimulates glycogen synthesis in the liver and muscle cells.

    • Also stimulates amino acid uptake and protein synthesis of muscle tissue


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    Glucagon molting in insects and crustaceans.

    • Produced by the  cells of the Islets of Langerhans

    • Stimulates change of glycogen to glucose in the liver.

    • Synthesis of glucose from lactic acid and non carbohydrate molecules such as fatty acids and amino acids

    • Causes  in blood glucose concentration

    hypoglycemic- low blood sugar; deficient in glucagon


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    Regulation of Blood Sugar Levels molting in insects and crustaceans.


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    Diabetes Melitus molting in insects and crustaceans.


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    Type I Diabetes molting in insects and crustaceans.hyposecretion of insulin insulin dependant juvenile onsetType II Diabetes late onset (adult) insensitivity of cells to insulin manage by exercise & diet


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    adrenal cortex molting in insects and crustaceans.

    adrenal medulla

    Adrenal Glands


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    Hormones of the Adrenal Medulla molting in insects and crustaceans.

    • Adrenalin (epinephrine): converts glycogen to glucose in liver

    • Noradrenalin (norepinephrine): increases blood pressure

  • (sympathetic nervous system)

    • Corticosteroids: glucose levels)


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    Hormones of the Adrenal Cortex molting in insects and crustaceans.

    • Glucocorticoids- cortisol

    • Decrease protein synthesis

    • Increase release and use of fatty acids

    • Stimulates the liver to produce glucose from non carb’s

    • Mineralcorticoids- aldosterone

    • Stimulates cells in kidney to reabsorb Na+ from filtrate

    • Increases water reabsorption in kidneys

    • Increases blood pressure

    • Sex Steroids- small amts (androgens)

    • Onset of puberty

    • Sex drive


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    Cushing’s Syndrome molting in insects and crustaceans.

    Hypersecretion of cortisone; may be caused by an ACTH releasing tumor in pituitary

    Symptoms: trunkal obesity and moon face, emotional instability

    Treatment: removal of adrenal gland and hormone replacement


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    Addison’s Disease molting in insects and crustaceans.

    Hyposecretion of glucocorticoids and mineral corticoids;

    Symptoms- wt loss, fatigue, dizziness, changes in mood and personality, low levels of plasma glucose and Na+ levels, high levels of K+

    Treatment- corticosteroid replacement therapy


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    Thymus molting in insects and crustaceans.

    Located anterior to the heart

    Produces- thymopoetin and thymosin helps direct maturation and specialization of T-lymphocytes (immunity)


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    Gonads molting in insects and crustaceans.

    Ovaries- produce estrogen and progesteroneresponsible for maturation of the reproductive organs and 2ndary sex characteristics in girls at puberty


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    Female Reproductive System molting in insects and crustaceans.


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    Gonads molting in insects and crustaceans.

    Testes- produce sperm and testosterone (initiates maturation of male repro organs and 2ndary sex characteristics in boys at puberty)


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    Male Reproductive System molting in insects and crustaceans.